It is proposed to continue our ongoing investigation of the radiation chemical properties of high energy heavy ion beams at the Lawrence Berkeley Laboratory in the context of a broad biomedical study. Aqueous solutions are being used as model systems because they have been well studied with other radiations. Solute systems chosen to throw light on the primary radiolysis products will be emphasized, and the yields measured as a function of beam penetration for carbon, neon and argon ions of several hundred MeV/amu. The chemical isotope effect on the hydrogen yield will also be measured. By such measurements it will be possible to gain information on the patterns of energy deposition for these radiations and hence provide basic information of value in assessing the optimum particle and energy for various diagnostic and therapeutic applications.